Yes not great coverage and very bland.
Could try some contrast adjustment, but even then it's looks very patchy because the images a mosaic of different times, so different ground temperatures I imagine.

ETM band 4 (IR1) could be interesting too, it would show a differentiation between vegetation and non-vegetation.

Other interesting thing you could try is to make false colour combinations
Like RGB with Bands 432 in the respective colour guns. (IR1, Red, Blue as listed on that site) In 432, vegetation comes out in very red, because of band 4 being in the red gun.

Some samples of different colour combinations on this site
http://www.geo.mtu.edu/rs/keweenaw/